Analytical testing for the amount of oil in a sample from coreflooding (water, CO2, or chemical) is an important step in determining the success of oil recovery. Oil in coreflooding can be present as an emulsion, an oil-water mixture, or in a clear oil phase, where the oil may be present in trace amounts. Determining the amount of oil in an oil-water mixture can be accomplished using a variety of common analytical methods. Common analytical methods include visual observation, near infra-red reflectance (NIR) spectroscopy, nuclear magnetic resonance (NMR), an OCMA-300 series oil content analyzer, and absorption spectroscopy.
Visual observation involves a sample of the oil-water mixture placed in a graduated cylinder and allowed to separate into an oil phase and a water phase. The amount of oil is then determined based on the height of the oil phase in the graduated cylinder. Visual observation is inaccurate when the amount of oil is less than 0.1 ml.
NIR spectroscopy requires a special instrument for the measurement and is sensitive to the changes in the texture of the samples. NMR also requires specialized equipment for measurement. An OCMA-300 series oil content analyzer can be used for measuring the oil content in emulsion samples. These methods all suffer from major drawbacks. First, they require expensive, complicated equipment and skilled operators, which adds to the expense of running a sample. Second, the methods can only be run on emulsion samples, not other samples of trace amounts of oil in water. Third, these methods can take significant time to obtain results on a given sample.